Dual chamber pacing with a single lead system: initial clinical results.

A new mode of biphasic pacing was used in 26 patients to assess the feasibility of atrial pacing by means of the floating atrial ring electrodes of a single lead VDD permanent pacing system. During implantation, atrial pacing was possible in 25 patients with a 1-ms total pulse duration, a mean atrial threshold of 1.70 +/- 0.60 V (range, 0.6-3.0), and a mean diaphragmatic threshold of 6.7 +/- 2.5 V (range, 2.5-10.0). At 3 months, the atrial threshold had increased beyond 4.8 V in three patients. In the 22 other patients, the mean atrial threshold was 2.2 +/- 0.5 V (range, 1.50-3.50) in the supine position and 2.5 +/- 0.8 V (range, 1.5-4.8) in the sitting position. Stable atrial capture without diaphragmatic stimulation was achieved in 76% of patients.